Utilizing techniques developed in our laboratory, we propose to mount a systematic in vitro and in vivo physiological and biomechanical analysis of muscle stem cell based tissue engineering treatment of stress urinary incontinence (SUI). SUI is a significant medical problem affecting approximately 25 million American women 1. Despite the high prevalence of SUI, there is very little treatment-oriented research utilizing tissue engineering techniques. Using such techniques, we propose to develop a truly physiologic sling, not from synthetic or cadaveric tissue, but rather an engineered, functional stem cell muscle scaffold that can be implanted to repair a damaged urethral sphincter.Hypothesis: 1) Muscle Derived Stem Cells (MDSC) improve the mechanical properties of small intestinal submucosa (SIS) scaffold in vitro. 2) MDSC/SIS suburethral sling improves continence in an in vivo rat model of SUI.The Key Aims of this grant include: 1) Establish the mechanisms underlying the alterations in biaxial mechanical properties of MDSC-seeded SIS: a) Establish the feasibility of seeding MDSC to SIS; b) Establish the long-term persistence of MDSC on SIS; and c) Evaluate the compliance properties of SIS alone and MDSC/SIS in vitro and in vivo with comprehensive mechanical testing at different time points. 2) Evaluate the contractile properties of MDSC/SIS: a) Test muscle and neurally evoked contractile properties of MDSC/SIS based on seeding different densities of MDSC onto SIS and culturing for 7 days; b) Using the best seeding density from 2a, test muscle and neurally evoked contractility properties of MDSC/SIS, culture in vitro at different time points; and c) Using the best seeding density from 2a, test muscle and neurally evoked contractility properties of MDSC/SIS cultured in vivo and at different time points. 3) Assess the functional outcome of MDSC/SIS versus SIS suburethral sling placement following simulated birth trauma: a) Assess the effect of SIS or MDSC/SIS suburethral slings on micturition during continuous cystometry; b) Assess the effect of SIS or MDSC/SIS on leak point pressure (LPP) using the reliable and sensitive vertical tilt intravesical pressure clamp method; c) Evaluate the immunohistology of implanted SIS and MDSC/SIS suburethral slings; and d) Retest the mechanical properties as well as muscle and neurally evoked contractile properties of MDSC/SIS suburethral slings following LPP testing for correlative purposes. By reengineering the deficient urinary sphincter through functional tissue engineering, we plan to significantly improve the treatment of SUI. We want to strongly emphasize that our research is in complete compliance with the federal guidelines on embryonic stem cell research. These stem cells have not been obtained from embryos (animal or human) or cell lines of embryonic stem cells.